Standing Room Only

In 2012 the global fertility rate - births per woman - was 2.5, compared to 2.0 needed for a stable population, assuming no stillbirths, and that all babies born survived to have children themselves. This means that every couple produced 2.5 children and over the course of a generation the population increases by a factor of

\[\frac{2.5}{2.0}=1.25\]

. In 2012 the world population was about 7 billion. After n generations the world population would be